Marine Weather and Tide Forecast for Herron Island, WA

SYNOPSIS
An upper level ridge with high pressure will leave one more nice day across western Washington today. An active weather pattern takes over from Monday through next weekend with multiple systems bringing in periods of precipitation across the region.
Temperatures will also drop several degrees, becoming more seasonal for this time in October.

SHORT TERM /TONIGHT THROUGH WEDNESDAY/
One more nice day to wrap up the weekend today. An upper level ridge over Alberta and eastern Washington begins to depart the area today to the east. One more dry and warm day is on tap this Sunday across western Washington (mostly clear skies with pockets of high cirrus in the air). Temperatures have broken 70 in several places already this afternoon (primarily in Puget Sound and west slopes of the Cascades), but with cooler and wet weather on the way, this may be the last 70 degree day for the foreseeable future.

The first of a series of weather makers is already visible on satellite just off the Pacific Coastline. A visible cloud band/moist conveyor belt stretches from the central Pacific (around Hawaii) up into a low just off the Alaska/British Columbia coastline. IVT analysis shows limited moisture funneling ahead of a low/trough for Monday into Tuesday. This will aid a cold front expected to pass through the region Monday into Tuesday for rain showers. This first "atmospheric river" is expected to be the weakest one this week, with limited QPF totals ranging from a tenth to a quarter in the lowlands, and up to around half an inch to an inch in the north Cascades, west Olympics and the coast. The rain will pass through Monday morning from west to east, and taper back going into Monday night to light showers. In addition, sneaker waves will be possible with this system, so beach goers should be on the lookout for high waves along the coastline.

A second, more vigorous trough digs off the Pacific Wednesday, and swings around a stronger cold front into the Pacific Northwest Wednesday. A 140 kt jet max pushes this front/trough inland with much cooler air behind. High temperatures will drop from the low 60s into the upper 50s Wednesday, with snow levels expected to drop to around 4,000 feet by late Wednesday. The jet will help funnel in moisture for additional rounds of precipitation throughout the day Wednesday. Given the stronger temperature gradient with this front, and cool air aloft, thunder will be possible on Wednesday. This will likely create localized heavier rainfall rates with any convection that is able to form. Flooding is not expected to be a concern with this next system, but rivers/streams will likely see rises with this system.
Additionally, many of the mountain areas above 4,000 feet will likely see accumulating snowfall, with potential of some of the snow sticking at Stevens Pass.

LONG TERM /THURSDAY THROUGH SUNDAY/
The Wednesday system will continue into Thursday with more rounds of precipitation continuing through Thursday night. Amounts are quite a bit spread from the mean, so it is too early to advertise potential amounts with this Wednesday/Thursday system (but will most likely be in the magnitude of an inch to a few inches, with the heavier amounts in the Cascades and the coast/Olympics).

The pattern becomes a little bit more uncertain next weekend. Most of the ensembles are showing another trough moving through Saturday and Sunday (alternative would be ridging in the Southwest underneath the trough). IVT analysis shows a more classic moisture plume moving in from the central Pacific into the Pacific Northwest. This will likely shift some between now and next weekend, but the potential exists for a more "classic" atmospheric river event next weekend with even more precipitation. The CPC does have a slight risk of heavy precipitation next weekend. This will be monitored throughout the week for potential hydro impacts.

HPR

AVIATION
Southwesterly flow aloft will persist tonight and throughout Monday as an upper level trough remains out over the eastern Pacific waters. Surface winds light and variable over much of W WA this evening before shifting more south to southwesterly overnight as speeds increase into the 4-8 kt range. The exception to this is HQM, where proximity of approaching front may give rise to westerly winds occasionally ranging 5-10 kts. Speeds here will remain consistent throughout the TAF period, though direction will become more southerly overnight.

Widespread VFR conditions this evening...already starting to see some high clouds associated with approaching front over the western half of the CWA at the time of this writing /745 PM PDT/...with some starting to spill over to the eastern banks of the Sound. Skies will fill in overnight as cigs lower down into widespread MVFR to IFR conditions in the 09-12Z time frame. As the front and the precip with it starts to move over terminals...starting in the west after 14Z...could see further reduction in cigs as well as vis restrictions. Once precip settles in over the area, will likely see cigs remain in the MVFR to IFR range for remainder of TAF period, even as precip transitions to more showery after afternoon FROPA.

KSEA...VFR conditions with high clouds overhead this evening and tonight. Conditions start to erode by 12Z as cigs expected to deteriorate down into MVFR conditions and stay put for remainder of TAF period. Precip in the late morning and early afternoon will likely drag cigs down a little bit more, although expected to remain within MVFR...albeit low-end. Some minor vis restrictions will also be possible. Light and variable winds overnight will persist before shifting more southerly and increasing slightly in speed...generally ranging 4-8 kts.

18

MARINE
Light southerly winds expected for the interior waters this evening and tonight with continued south to southeast winds for the Coastal Waters. Southerly winds will then increase overnight into Monday for all area waters as a front moves across Western Washington. Speeds remain sufficient to sustain inherited SCAs for the Coastal Waters and Admiralty Inlet. Some spillover may be possible for waters adjacent to Admiralty Inlet, however SCA speeds will be limited in those areas and as such, will support decision to keep those waters out of any headlines for now. Similarly, some spillover from the Coastal waters into the West Entrance to the Strait may allow wind speeds near Neah Bay to bump up against or occasionally meet SCA criteria, but again, not widespread enough for including the entire zone into the advisory area. Will advise next shift to make sure forecast remains consistent as a slight nudge upward for any of these adjacent waters may allow for expansion of advisory area.

Winds expected to ease Monday night through Tuesday. Another, potentially stronger front, is expected to move through the area Tuesday night into Wednesday. Additional headlines possible for increasing south to southwest winds during this period. A post- frontal westerly push is forecast on Wednesday for the Strait of Juan de Fuca as well.

Seas 6 to 8 feet building to 10 to 13 feet later tonight into Monday. As such, Small Craft Advisories continue for the Coastal Waters due to seas Monday into Monday night. 10 ft seas possible into westernmost portion of the West Entrance to the Strait, however a limited eastward penetration suggests that a headline for the entire zone does not appear to be warranted at this time. Seas are expected to then briefly subside below 10 feet later Tuesday before increasing to near 10 feet Wednesday and potentially into Thursday as the more active and unsettled weather pattern continues.

18/Kristell



SEW WATCHES/WARNINGS/ADVISORIES
WA...None.
PZ...Small Craft Advisory from 8 AM to 5 PM PDT Monday for Grays Harbor Bar.

Small Craft Advisory from 5 AM to 11 AM PDT Monday for Admiralty Inlet.

Small Craft Advisory until 11 PM PDT Monday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm.

Small Craft Advisory from 5 AM to 11 PM PDT Monday for Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Small Craft Advisory until 8 AM PDT Tuesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.